Russ immediately realized why the polar bears (Ursus maritimus) "of all ages, sexes and sizes" had congregated there: They were feasting on a dead bowhead whale (Balaena mysticetus), he wrote in the blog post. Russ counted more than 150 polar bears, although a statement issued by the Wrangel Island State Nature Reserve put that estimate at closer to 230 bears.

Intrigued, the tour group left their boat, the Akademik Shokalskiy (the same vessel that got stuck in Antarctic sea ice in December 2013) and boarded smaller vessels known as zodiacs to get a closer look at the seemingly ravenous bears.

"That is the memory we will all carry with us," Russ wrote. "There are no words to describe it."

It's possible so many bears attended the impromptu picnic because they smelled the rotting whale. Polar bears can smell seals up to 20 miles (32 kilometers) away, according to the San Diego Zoo. When they're not eating beached whales, the bears are known to eat ringed seals, walrus, caribou, grass and seaweed, the San Diego Zoo says.

These polar bears got a whale of a meal.

Credit: Alexander Gruzdev/Wrangel Island State Nature Reserve

Polar bears are listed as vulnerable to extinction, largely because human-made climate change is melting the Arctic sea ice where they live, according to the International Union for Conservation of Nature (IUCN).

It's unclear, however, whether climate change had made these particular bears hungrier than usual. The frequency of starving polar bears is expected to increase as the climate warms and sea ice declines — not just because of climate change directly, but because ice loss is taking away seals, their main food source, Steven Amstrup, chief scientist at Polar Bears International, a nonprofit research organization dedicated to studying polar bears, told Live Science in 2015.

The bowhead whale is listed as an "animal of least concern," meaning it is not at risk, the IUCN says.

As a senior writer for Live Science, Laura Geggel covers general science, including the environment and amazing animals. She has written for The New York Times, Scholastic, Popular Science and Spectrum, a site covering autism research. Laura grew up in Seattle and studied English literature and psychology at Washington University in St. Louis before completing her graduate degree in science writing at NYU. When not writing, you'll find Laura playing Ultimate Frisbee. Follow Laura on Google+.